/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.text.VttTextParser');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.text.Cue');
goog.require('shaka.text.CueRegion');
goog.require('shaka.text.TextEngine');
goog.require('shaka.util.Error');
goog.require('shaka.util.StringUtils');
goog.require('shaka.util.TextParser');
goog.require('shaka.util.XmlUtils');
/**
* @implements {shaka.extern.TextParser}
* @export
*/
shaka.text.VttTextParser = class {
/**
* @override
* @export
*/
parseInit(data) {
goog.asserts.assert(false, 'VTT does not have init segments');
}
/**
* @override
* @export
*/
parseMedia(data, time) {
const VttTextParser = shaka.text.VttTextParser;
// Get the input as a string. Normalize newlines to \n.
let str = shaka.util.StringUtils.fromUTF8(data);
str = str.replace(/\r\n|\r(?=[^\n]|$)/gm, '\n');
const blocks = str.split(/\n{2,}/m);
if (!/^WEBVTT($|[ \t\n])/m.test(blocks[0])) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_TEXT_HEADER);
}
// NOTE: "periodStart" is the timestamp offset applied via TextEngine.
// It is no longer closely tied to periods, but the name stuck around.
let offset = time.periodStart;
if (blocks[0].includes('X-TIMESTAMP-MAP')) {
// https://bit.ly/2K92l7y
// The 'X-TIMESTAMP-MAP' header is used in HLS to align text with
// the rest of the media.
// The header format is 'X-TIMESTAMP-MAP=MPEGTS:n,LOCAL:m'
// (the attributes can go in any order)
// where n is MPEG-2 time and m is cue time it maps to.
// For example 'X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000'
// means an offset of 10 seconds
// 900000/MPEG_TIMESCALE - cue time.
const cueTimeMatch =
blocks[0].match(/LOCAL:((?:(\d{1,}):)?(\d{2}):(\d{2})\.(\d{3}))/m);
const mpegTimeMatch = blocks[0].match(/MPEGTS:(\d+)/m);
if (cueTimeMatch && mpegTimeMatch) {
const parser = new shaka.util.TextParser(cueTimeMatch[1]);
const cueTime = shaka.text.VttTextParser.parseTime_(parser);
if (cueTime == null) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_TEXT_HEADER);
}
let mpegTime = Number(mpegTimeMatch[1]);
const mpegTimescale = shaka.text.VttTextParser.MPEG_TIMESCALE_;
const rolloverSeconds =
shaka.text.VttTextParser.TS_ROLLOVER_ / mpegTimescale;
let segmentStart = time.segmentStart;
while (segmentStart >= rolloverSeconds) {
segmentStart -= rolloverSeconds;
mpegTime += shaka.text.VttTextParser.TS_ROLLOVER_;
}
// Apple-encoded HLS content uses absolute timestamps, so assume the
// presence of the map tag means the content uses absolute timestamps.
offset = time.periodStart + mpegTime / mpegTimescale - cueTime;
}
}
// Parse VTT regions.
/* !Array.<!shaka.extern.CueRegion> */
const regions = [];
for (const line of blocks[0].split('\n')) {
if (/^Region:/.test(line)) {
const region = VttTextParser.parseRegion_(line);
regions.push(region);
}
}
/** @type {!Map.<string, shaka.text.Cue>} */
const styles = new Map();
VttTextParser.addDefaultTextColor_(styles);
// Parse cues.
const ret = [];
for (const block of blocks.slice(1)) {
const lines = block.split('\n');
VttTextParser.parseStyle_(lines, styles);
const cue = VttTextParser.parseCue_(lines, offset, regions, styles);
if (cue) {
ret.push(cue);
}
}
return ret;
}
/**
* Add default color
*
* @param {!Map.<string, shaka.text.Cue>} styles
* @private
*/
static addDefaultTextColor_(styles) {
const textColor = shaka.text.Cue.defaultTextColor;
for (const [key, value] of Object.entries(textColor)) {
const cue = new shaka.text.Cue(0, 0, '');
cue.color = value;
styles.set(key, cue);
}
const bgColor = shaka.text.Cue.defaultTextBackgroundColor;
for (const [key, value] of Object.entries(bgColor)) {
const cue = new shaka.text.Cue(0, 0, '');
cue.backgroundColor = value;
styles.set(key, cue);
}
}
/**
* Parses a string into a Region object.
*
* @param {string} text
* @return {!shaka.extern.CueRegion}
* @private
*/
static parseRegion_(text) {
const VttTextParser = shaka.text.VttTextParser;
const parser = new shaka.util.TextParser(text);
// The region string looks like this:
// Region: id=fred width=50% lines=3 regionanchor=0%,100%
// viewportanchor=10%,90% scroll=up
const region = new shaka.text.CueRegion();
// Skip 'Region:'
parser.readWord();
parser.skipWhitespace();
let word = parser.readWord();
while (word) {
if (!VttTextParser.parseRegionSetting_(region, word)) {
shaka.log.warning(
'VTT parser encountered an invalid VTTRegion setting: ', word,
' The setting will be ignored.');
}
parser.skipWhitespace();
word = parser.readWord();
}
return region;
}
/**
* Parses a style block into a Cue object.
*
* @param {!Array.<string>} text
* @param {!Map.<string, shaka.text.Cue>} styles
* @private
*/
static parseStyle_(text, styles) {
// Skip empty blocks.
if (text.length == 1 && !text[0]) {
return;
}
// Skip comment blocks.
if (/^NOTE($|[ \t])/.test(text[0])) {
return;
}
// Only style block are allowed.
if (text[0] != 'STYLE') {
return;
}
if (!text[1].includes('::cue')) {
return;
}
let styleSelector = 'global';
// Look for what is within parentisesis. For example:
// <code>:: cue (b) {</code>, what we are looking for is <code>b</code>
const selector = text[1].match(/\((.*)\)/);
if (selector) {
styleSelector = selector.pop();
}
// We start at 2 to avoid '::cue' and end earlier to avoid '}'
let propertyLines = text.slice(2, -1);
if (text[1].includes('}')) {
const payload = /\{(.*?)\}/.exec(text[1]);
if (payload) {
propertyLines = payload[1].split(';');
}
}
const cue = new shaka.text.Cue(0, 0, '');
let validStyle = false;
for (let i = 0; i < propertyLines.length; i++) {
// We look for CSS properties. As a general rule they are separated by
// <code>:</code>. Eg: <code>color: red;</code>
const lineParts = /^\s*([^:]+):\s*(.*)/.exec(propertyLines[i]);
if (lineParts) {
const name = lineParts[1].trim();
const value = lineParts[2].trim().replace(';', '');
switch (name) {
case 'background-color':
validStyle = true;
cue.backgroundColor = value;
break;
case 'color':
validStyle = true;
cue.color = value;
break;
case 'font-family':
validStyle = true;
cue.fontFamily = value;
break;
case 'font-size':
validStyle = true;
cue.fontSize = value;
break;
case 'font-weight':
if (parseInt(value, 10) >= 700) {
validStyle = true;
cue.fontWeight = shaka.text.Cue.fontWeight.BOLD;
}
break;
case 'font-style':
switch (value) {
case 'normal':
validStyle = true;
cue.fontStyle = shaka.text.Cue.fontStyle.NORMAL;
break;
case 'italic':
validStyle = true;
cue.fontStyle = shaka.text.Cue.fontStyle.ITALIC;
break;
case 'oblique':
validStyle = true;
cue.fontStyle = shaka.text.Cue.fontStyle.OBLIQUE;
break;
}
break;
case 'opacity':
validStyle = true;
cue.opacity = parseFloat(value);
break;
case 'white-space':
validStyle = true;
cue.wrapLine = value != 'noWrap';
break;
default:
shaka.log.warning('VTT parser encountered an unsupported style: ',
lineParts);
break;
}
}
}
if (validStyle) {
styles.set(styleSelector, cue);
}
}
/**
* Parses a text block into a Cue object.
*
* @param {!Array.<string>} text
* @param {number} timeOffset
* @param {!Array.<!shaka.extern.CueRegion>} regions
* @param {!Map.<string, shaka.text.Cue>} styles
* @return {shaka.text.Cue}
* @private
*/
static parseCue_(text, timeOffset, regions, styles) {
const VttTextParser = shaka.text.VttTextParser;
// Skip empty blocks.
if (text.length == 1 && !text[0]) {
return null;
}
// Skip comment blocks.
if (/^NOTE($|[ \t])/.test(text[0])) {
return null;
}
// Skip style blocks.
if (text[0] == 'STYLE') {
return null;
}
let id = null;
if (!text[0].includes('-->')) {
id = text[0];
text.splice(0, 1);
}
// Parse the times.
const parser = new shaka.util.TextParser(text[0]);
let start = VttTextParser.parseTime_(parser);
const expect = parser.readRegex(/[ \t]+-->[ \t]+/g);
let end = VttTextParser.parseTime_(parser);
if (start == null || expect == null || end == null) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_TEXT_CUE,
'Could not parse cue time range in WebVTT');
}
start += timeOffset;
end += timeOffset;
// Get the payload.
const payload = text.slice(1).join('\n').trim();
let cue = null;
if (styles.has('global')) {
cue = styles.get('global').clone();
cue.startTime = start;
cue.endTime = end;
cue.payload = '';
} else {
cue = new shaka.text.Cue(start, end, '');
}
VttTextParser.parseCueStyles(payload, cue, styles);
// Parse optional settings.
parser.skipWhitespace();
let word = parser.readWord();
while (word) {
if (!VttTextParser.parseCueSetting(cue, word, regions)) {
shaka.log.warning('VTT parser encountered an invalid VTT setting: ',
word,
' The setting will be ignored.');
}
parser.skipWhitespace();
word = parser.readWord();
}
if (id != null) {
cue.id = id;
}
return cue;
}
/**
* Parses a WebVTT styles from the given payload.
*
* @param {string} payload
* @param {!shaka.text.Cue} rootCue
* @param {!Map.<string, shaka.text.Cue>} styles
*/
static parseCueStyles(payload, rootCue, styles) {
const VttTextParser = shaka.text.VttTextParser;
if (styles.size === 0) {
VttTextParser.addDefaultTextColor_(styles);
}
payload = VttTextParser.replaceColorPayload_(payload);
const xmlPayload = '<span>' + payload + '</span>';
const element = shaka.util.XmlUtils.parseXmlString(xmlPayload, 'span');
if (element) {
/** @type {!Array.<!shaka.extern.Cue>} */
const cues = [];
const childNodes = element.childNodes;
if (childNodes.length == 1) {
const childNode = childNodes[0];
if (childNode.nodeType == Node.TEXT_NODE ||
childNode.nodeType == Node.CDATA_SECTION_NODE) {
rootCue.payload = payload;
return;
}
}
for (const childNode of childNodes) {
VttTextParser.generateCueFromElement_(
childNode, rootCue, cues, styles);
}
rootCue.nestedCues = cues;
} else {
shaka.log.warning('The cue\'s markup could not be parsed: ', payload);
rootCue.payload = payload;
}
}
/**
* Converts color end tag to be valid for xml parsing
* For example,
* input: <c.yellow.bg_blue>Yellow text on blue bg</c>
* output: <c.yellow.bg_blue>Yellow text on blue bg</c.yellow.bg_blue>
*
* Returns original payload if invalid tag is found.
* Invalid tag example: <c.yellow><b>Example</c></b>
*
* @param {string} payload
* @return {string} processed payload
* @private
*/
static replaceColorPayload_(payload) {
const names = [];
let nameStart = -1;
let newPayload = '';
for (let i = 0; i < payload.length; i++) {
if (payload[i] === '/') {
const end = payload.indexOf('>', i);
if (end <= i) {
return payload;
}
const tagEnd = payload.substring(i + 1, end);
const tagStart = names.pop();
if (!tagEnd || !tagStart) {
return payload;
} else if (tagStart === tagEnd) {
newPayload += '/' + tagEnd + '>';
i += tagEnd.length + 1;
} else {
if (!tagStart.startsWith('c.') || tagEnd !== 'c') {
return payload;
}
newPayload += '/' + tagStart + '>';
i += tagEnd.length + 1;
}
} else {
if (payload[i] === '<') {
nameStart = i + 1;
} else if (payload[i] === '>') {
if (nameStart > 0) {
names.push(payload.substr(nameStart, i - nameStart));
nameStart = -1;
}
}
newPayload += payload[i];
}
}
return newPayload;
}
/**
* @param {string} value
* @param {string} defaultValue
* @private
*/
static getOrDefault_(value, defaultValue) {
if (value && value.length > 0) {
return value;
}
return defaultValue;
}
/**
* Merges values created in parseStyle_
* @param {!shaka.extern.Cue} cue
* @param {shaka.extern.Cue} refCue
* @private
*/
static mergeStyle_(cue, refCue) {
if (!refCue) {
return;
}
const VttTextParser = shaka.text.VttTextParser;
// Overwrites if new value string length > 0
cue.backgroundColor = VttTextParser.getOrDefault_(
refCue.backgroundColor, cue.backgroundColor);
cue.color = VttTextParser.getOrDefault_(
refCue.color, cue.color);
cue.fontFamily = VttTextParser.getOrDefault_(
refCue.fontFamily, cue.fontFamily);
cue.fontSize = VttTextParser.getOrDefault_(
refCue.fontSize, cue.fontSize);
// Overwrite with new values as unable to determine
// if new value is set or not
cue.fontWeight = refCue.fontWeight;
cue.fontStyle = refCue.fontStyle;
cue.opacity = refCue.opacity;
cue.wrapLine = refCue.wrapLine;
}
/**
* @param {!Node} element
* @param {!shaka.text.Cue} rootCue
* @param {Array.<!shaka.extern.Cue>} cues
* @param {!Map.<string, shaka.text.Cue>} styles
* @private
*/
static generateCueFromElement_(element, rootCue, cues, styles) {
const VttTextParser = shaka.text.VttTextParser;
const nestedCue = rootCue.clone();
if (element.nodeType === Node.ELEMENT_NODE && element.nodeName) {
const bold = shaka.text.Cue.fontWeight.BOLD;
const italic = shaka.text.Cue.fontStyle.ITALIC;
const underline = shaka.text.Cue.textDecoration.UNDERLINE;
const tags = element.nodeName.split(/[ .]+/);
for (const tag of tags) {
if (styles.has(tag)) {
VttTextParser.mergeStyle_(nestedCue, styles.get(tag));
}
switch (tag) {
case 'b':
nestedCue.fontWeight = bold;
break;
case 'i':
nestedCue.fontStyle = italic;
break;
case 'u':
nestedCue.textDecoration.push(underline);
break;
default:
break;
}
}
}
const isTextNode = shaka.util.XmlUtils.isText(element);
if (isTextNode) {
// Trailing line breaks may lost when convert cue to HTML tag
// Need to insert line break cue to preserve line breaks
const textArr = element.textContent.split('\n');
let isFirst = true;
for (const text of textArr) {
if (!isFirst) {
const lineBreakCue = rootCue.clone();
lineBreakCue.lineBreak = true;
cues.push(lineBreakCue);
}
if (text.length > 0) {
const textCue = nestedCue.clone();
textCue.payload = text;
cues.push(textCue);
}
isFirst = false;
}
} else {
for (const childNode of element.childNodes) {
VttTextParser.generateCueFromElement_(
childNode, nestedCue, cues, styles);
}
}
}
/**
* Parses a WebVTT setting from the given word.
*
* @param {!shaka.text.Cue} cue
* @param {string} word
* @param {!Array.<!shaka.text.CueRegion>} regions
* @return {boolean} True on success.
*/
static parseCueSetting(cue, word, regions) {
const VttTextParser = shaka.text.VttTextParser;
let results = null;
if ((results = /^align:(start|middle|center|end|left|right)$/.exec(word))) {
VttTextParser.setTextAlign_(cue, results[1]);
} else if ((results = /^vertical:(lr|rl)$/.exec(word))) {
VttTextParser.setVerticalWritingMode_(cue, results[1]);
} else if ((results = /^size:([\d.]+)%$/.exec(word))) {
cue.size = Number(results[1]);
} else if ((results =
/^position:([\d.]+)%(?:,(line-left|line-right|center|start|end))?$/
.exec(word))) {
cue.position = Number(results[1]);
if (results[2]) {
VttTextParser.setPositionAlign_(cue, results[2]);
}
} else if ((results = /^region:(.*)$/.exec(word))) {
const region = VttTextParser.getRegionById_(regions, results[1]);
if (region) {
cue.region = region;
}
} else {
return VttTextParser.parsedLineValueAndInterpretation_(cue, word);
}
return true;
}
/**
*
* @param {!Array.<!shaka.text.CueRegion>} regions
* @param {string} id
* @return {?shaka.text.CueRegion}
* @private
*/
static getRegionById_(regions, id) {
const regionsWithId = regions.filter((region) => {
return region.id == id;
});
if (!regionsWithId.length) {
shaka.log.warning('VTT parser could not find a region with id: ',
id,
' The region will be ignored.');
return null;
}
goog.asserts.assert(regionsWithId.length == 1,
'VTTRegion ids should be unique!');
return regionsWithId[0];
}
/**
* Parses a WebVTTRegion setting from the given word.
*
* @param {!shaka.text.CueRegion} region
* @param {string} word
* @return {boolean} True on success.
* @private
*/
static parseRegionSetting_(region, word) {
let results = null;
if ((results = /^id=(.*)$/.exec(word))) {
region.id = results[1];
} else if ((results = /^width=(\d{1,2}|100)%$/.exec(word))) {
region.width = Number(results[1]);
} else if ((results = /^lines=(\d+)$/.exec(word))) {
region.height = Number(results[1]);
region.heightUnits = shaka.text.CueRegion.units.LINES;
} else if ((results = /^regionanchor=(\d{1,2}|100)%,(\d{1,2}|100)%$/
.exec(word))) {
region.regionAnchorX = Number(results[1]);
region.regionAnchorY = Number(results[2]);
} else if ((results = /^viewportanchor=(\d{1,2}|100)%,(\d{1,2}|100)%$/
.exec(word))) {
region.viewportAnchorX = Number(results[1]);
region.viewportAnchorY = Number(results[2]);
} else if ((results = /^scroll=up$/.exec(word))) {
region.scroll = shaka.text.CueRegion.scrollMode.UP;
} else {
return false;
}
return true;
}
/**
* @param {!shaka.text.Cue} cue
* @param {string} align
* @private
*/
static setTextAlign_(cue, align) {
const Cue = shaka.text.Cue;
if (align == 'middle') {
cue.textAlign = Cue.textAlign.CENTER;
} else {
goog.asserts.assert(align.toUpperCase() in Cue.textAlign,
align.toUpperCase() +
' Should be in Cue.textAlign values!');
cue.textAlign = Cue.textAlign[align.toUpperCase()];
}
}
/**
* @param {!shaka.text.Cue} cue
* @param {string} align
* @private
*/
static setPositionAlign_(cue, align) {
const Cue = shaka.text.Cue;
if (align == 'line-left' || align == 'start') {
cue.positionAlign = Cue.positionAlign.LEFT;
} else if (align == 'line-right' || align == 'end') {
cue.positionAlign = Cue.positionAlign.RIGHT;
} else {
cue.positionAlign = Cue.positionAlign.CENTER;
}
}
/**
* @param {!shaka.text.Cue} cue
* @param {string} value
* @private
*/
static setVerticalWritingMode_(cue, value) {
const Cue = shaka.text.Cue;
if (value == 'lr') {
cue.writingMode = Cue.writingMode.VERTICAL_LEFT_TO_RIGHT;
} else {
cue.writingMode = Cue.writingMode.VERTICAL_RIGHT_TO_LEFT;
}
}
/**
* @param {!shaka.text.Cue} cue
* @param {string} word
* @return {boolean}
* @private
*/
static parsedLineValueAndInterpretation_(cue, word) {
const Cue = shaka.text.Cue;
let results = null;
if ((results = /^line:([\d.]+)%(?:,(start|end|center))?$/.exec(word))) {
cue.lineInterpretation = Cue.lineInterpretation.PERCENTAGE;
cue.line = Number(results[1]);
if (results[2]) {
goog.asserts.assert(
results[2].toUpperCase() in Cue.lineAlign,
results[2].toUpperCase() + ' Should be in Cue.lineAlign values!');
cue.lineAlign = Cue.lineAlign[results[2].toUpperCase()];
}
} else if ((results =
/^line:(-?\d+)(?:,(start|end|center))?$/.exec(word))) {
cue.lineInterpretation = Cue.lineInterpretation.LINE_NUMBER;
cue.line = Number(results[1]);
if (results[2]) {
goog.asserts.assert(
results[2].toUpperCase() in Cue.lineAlign,
results[2].toUpperCase() + ' Should be in Cue.lineAlign values!');
cue.lineAlign = Cue.lineAlign[results[2].toUpperCase()];
}
} else {
return false;
}
return true;
}
/**
* Parses a WebVTT time from the given parser.
*
* @param {!shaka.util.TextParser} parser
* @return {?number}
* @private
*/
static parseTime_(parser) {
// 00:00.000 or 00:00:00.000 or 0:00:00.000 or
// 00:00.00 or 00:00:00.00 or 0:00:00.00
const regexExpresion = /(?:(\d{1,}):)?(\d{2}):(\d{2})\.(\d{2,3})/g;
const results = parser.readRegex(regexExpresion);
if (results == null) {
return null;
}
// This capture is optional, but will still be in the array as undefined,
// in which case it is 0.
const hours = Number(results[1]) || 0;
const minutes = Number(results[2]);
const seconds = Number(results[3]);
const milliseconds = Number(results[4]);
if (minutes > 59 || seconds > 59) {
return null;
}
return (milliseconds / 1000) + seconds + (minutes * 60) + (hours * 3600);
}
};
/**
* @const {number}
* @private
*/
shaka.text.VttTextParser.MPEG_TIMESCALE_ = 90000;
/**
* At this value, timestamps roll over in TS content.
* @const {number}
* @private
*/
shaka.text.VttTextParser.TS_ROLLOVER_ = 0x200000000;
shaka.text.TextEngine.registerParser(
'text/vtt', () => new shaka.text.VttTextParser());
shaka.text.TextEngine.registerParser(
'text/vtt; codecs="vtt"', () => new shaka.text.VttTextParser());
shaka.text.TextEngine.registerParser(
'text/vtt; codecs="wvtt"', () => new shaka.text.VttTextParser());